[PATCH 2/2] cpufreq: intel_pstate: enable HWP after resumed

[PATCH 2/2] cpufreq: intel_pstate: enable HWP after resumed

[Yu Chen]

When maxcpus=1 is appended the BP is responsible
for re-enabling the HWP - because currently only
the APs invoke intel_pstate_hwp_enable() during
their online process - which might put the system
into unstable state after resume.

Fix this by enabling the HWP explicitly on BP during
resume.

Reported-by: Doug Smythies <dsmythies@telus.net>
Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Yu Chen <yu.c.chen@intel.com>
---
 drivers/cpufreq/intel_pstate.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 93a0e88bef76..89f637e8439c 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -779,6 +779,8 @@ static int intel_pstate_hwp_save_state(struct cpufreq_policy *policy)
 	return 0;
 }
 
+static void intel_pstate_hwp_enable(struct cpudata *cpudata);
+
 static int intel_pstate_resume(struct cpufreq_policy *policy)
 {
 	if (!hwp_active)
@@ -786,6 +788,8 @@ static int intel_pstate_resume(struct cpufreq_policy *policy)
 
 	mutex_lock(&intel_pstate_limits_lock);
 
+	if (!policy->cpu)
+		intel_pstate_hwp_enable(all_cpu_data[policy->cpu]);
 	all_cpu_data[policy->cpu]->epp_policy = 0;
 	intel_pstate_hwp_set(policy->cpu);
 
-- 
2.13.6

Re: [PATCH 2/2] cpufreq: intel_pstate: enable HWP after resumed

[Rafael J. Wysocki]

On Monday, January 29, 2018 3:27:57 AM CET Yu Chen wrote:
> When maxcpus=1 is appended the BP is responsible
> for re-enabling the HWP - because currently only
> the APs invoke intel_pstate_hwp_enable() during
> their online process - which might put the system
> into unstable state after resume.
> 
> Fix this by enabling the HWP explicitly on BP during
> resume.
> 
> Reported-by: Doug Smythies <dsmythies@telus.net>
> Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Signed-off-by: Yu Chen <yu.c.chen@intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 93a0e88bef76..89f637e8439c 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -779,6 +779,8 @@ static int intel_pstate_hwp_save_state(struct cpufreq_policy *policy)
>  	return 0;
>  }
>  
> +static void intel_pstate_hwp_enable(struct cpudata *cpudata);
> +
>  static int intel_pstate_resume(struct cpufreq_policy *policy)
>  {
>  	if (!hwp_active)
> @@ -786,6 +788,8 @@ static int intel_pstate_resume(struct cpufreq_policy *policy)
>  
>  	mutex_lock(&intel_pstate_limits_lock);
>  
> +	if (!policy->cpu)
> +		intel_pstate_hwp_enable(all_cpu_data[policy->cpu]);
>  	all_cpu_data[policy->cpu]->epp_policy = 0;
>  	intel_pstate_hwp_set(policy->cpu);
>  
> 

I've applied this one (with minor modifications) as a temporary measure, but
it is based on the CPU0=BP assumption which may not be the case.